Similar-distance grouping (SDG) [1]} is another candidate scheme for THz-NOMA clustering. In SDG, users are clustered according to their distances from the BS; the nearest two users form the first group, the second nearest the second group, etc. As opposed to strong-weak user pairing, SDG pairs a strong user with another strong user and vice versa. Consequently, spectrum allocation can be facilitated, where weak-user groups get assigned sub-bands suffering from less path loss (more details in the next subsection).
